Accurate position information for mobile stations, such as cellular or other wireless communication devices, is becoming prevalent in the communications industry. The Global Positioning System (GPS) offers an approach to providing wireless mobile station position determination. A GPS user can derive precise navigation information including three-dimensional position, velocity and time through information gained from satellite vehicles (SVs) in orbit around the earth. The signals that are received from the SVs are typically rather weak. Therefore, in order to determine the position of the receiver, the receiver must be sufficiently sensitive to acquire these weak signals and interpret the information that is represented by them.
One limitation of current GPS receivers is that their operation is limited to situations in which multiple satellites are clearly in view, without obstructions, and where a good quality antenna is properly positioned to receive such signals. As such, they normally are unusable in areas with blockage conditions, such as where there is significant foliage or building blockage (e.g., urban canyons) and, particularly, within buildings.
One of the major holdups in implementation of current indoor location based services based on wireless signals is the prerequisites needed to enable such a system. At a minimum, the indoor area has to be covered either by wireless access points deployed in the indoor area or the indoor area has to be covered by wireless access points deployed in the surrounding buildings that cover the indoor area. In addition, prior knowledge of the locations mapped to the wireless signal fingerprints, which enable the location based system, are needed on the handset to enable a location fix. In addition many of the useful services, such as routing and POI (Point of Interest) search that harness this system, require a base map of the current location. This can be a significant problem as mapping and manually locating all access points and points of interest can be an extremely tedious, time consuming and error prone task.